The present invention relates to an output power control system of a microwave oven and, more particularly, an output control system of a microwave oven periodically detecting open or close state of a door of the microwave oven. a magnetron tube for oscillation radiates microwaves in cooking with the door being closed. Radiation of the microwaves ceases when the door is open, even in the cooking, and, when the door is again closed, the radiation restarts.
A recent microwave oven employs an LSI (large scale integrated) circuit to more satisfactorily control the microwave oven, compared to the conventional. In control of such an oven, the control system periodically detects some conditions: the timer is set at a desired time; a start button is pushed; the door is closed. When these conditions are satisfied, the control system causes the magnetron to oscillate. On the other hand, when the conditions are not satisfied, it ceases oscillation of the magnetron. In the control system of the type periodically detecting the open and closed states of the door, when the door is closed at the first detection point, the magnetron tube starts it oscillation and continues it till the next detection point. If the door is manually opened between the first and second detection points, the magnetron continues its oscillation from the door opening point to the succeeding detection point. That is, in this case, the microwaves leak to the exterior and the leakage is dangerious and wasteful of power. Therefore, in such a case, it is necessary to immediately stop the oscillation when the door is opened. One of the control systems for the microwave oven, which periodically detects the open and closed states of the door, is disclosed in the U.S. Patent Application assigned to Tokyo Shibaura Electric Co., Ltd., bearing Ser. No. 887,221, filed on Mar. 16, 1978, by Sadao Zushi and Yoshio Oida, entitled "Microwave Ovens".
Accordingly, an object of the invention is to provide an output power control system for a microwave oven of the type periodically detecting the open and closed states of the door, which can immediately stop oscillation of a magnetron tube when the door is opened in cooking.